1. Field of the Invention
The present invention relates to a radio frequency (RF) signal transmission/reception apparatus and a radio frequency signal transmission/reception method, and more particularly, to a radio frequency (RF) signal transmission/reception apparatus which has a simple structure and excellent signal transmission/reception performance, and a radio frequency signal transmission/reception method using the same.
2. Discussion of the Related Art
Nowadays, converged in a mobile phone are various wireless communication schemes, for example, wireless communication schemes such as global system for mobile communication (GSM), code division multiple access (CDMA) and wideband code division multiple access (WCDMA), wireless communication schemes such as wireless local area network (WLAN) and worldwide interoperability for microwave access (Wimax), wireless communication schemes such as ultra wideband (UWB) and BLUETOOTH, global positioning system (GPS)-based wireless communication schemes, and so forth. As a result, there is an increasing demand for a wireless transmission/reception chip capable of processing various communication schemes which is small in size, excellent in reception performance and low in power consumption. Moreover, the provision of many wireless communication services involves an increasing demand for a wireless transmission/reception chip that overcomes interference from external signals and is stable in wireless environments.
FIG. 1 shows an example of a radio frequency signal transmission/reception apparatus. As shown in this drawing, the conventional apparatus for transmitting and receiving a radio frequency (RF) signal comprises an RF duplexer 10 connected to an antenna, a reception signal processor 20 and transmission signal processor 30 connected in common to the RF duplexer 10, and a frequency synthesizer 40 and a modem 50 connected in common to the reception signal processor 20 and the transmission signal processor 30. The operation of the conventional radio frequency signal transmission/reception apparatus will hereinafter be described with reference to FIG. 1.
The RF duplexer 10 transmits or receives an RF signal such that it is passed with low loss between the antenna and the reception signal processor 20 or between the transmission signal processor 30 and the antenna.
The RF duplexer 10 includes an RF reception band pass filter and an RF transmission band pass filter. The RF reception band pass filter has one terminal connected to the antenna and the other terminal connected to the reception signal processor 20, and the RF transmission band pass filter has one terminal connected to the transmission signal processor 30 and the other terminal connected to the antenna. An RF signal passed through the antenna and reception signal processor 20 and an RF signal passed through the transmission signal processor 30 can be separated from each other to a very high frequency isolation degree based on characteristics of the pass filters included in the RF duplexer 10.
Accordingly, the RF duplexer 10 isolates an RF signal to be inputted to the reception signal processor 20 and an RF signal outputted from the transmission signal processor 30 from each other so that the RF signal transmission/reception apparatus can transmit and receive the RF signals at the same time.
The RF duplexer 10 may be made with a film bulk acoustic resonator (FBAR) filter, bulk acoustic wave (BAW) filter, dielectric filter, lumped LC filter, low temperature co-fired ceramic (LTCC) filter, or the like.
The reception signal processor 20 amplifies a signal received through the antenna and RF duplexer 10, performs a frequency conversion, channel filtering and variable gain control with respect to the amplified signal and outputs the resulting signal to the modem 50.
To this end, the reception signal processor 20 includes a low-noise amplifier 21, a first mixer 22, a first filter 23, and a first variable gain amplifier (VGA) 24.
The low-noise amplifier 21 amplifies the received signal, and the first mixer 22 down-converts the frequency of an RF signal from the low-noise amplifier 21 using an oscillation signal from the frequency synthesizer 40.
The first filter 23 filters an output signal from the first mixer 22 at an intermediate frequency (IF) band or baseband, and the first VGA 24 performs a variable amplification with respect to an IF band signal or baseband signal from the first filter 23 and outputs the resulting signal to the modem 50.
In order to transmit a signal received from the modem 50, the transmission signal processor 30 performs a variable amplification, channel filtering, frequency conversion and power amplification with respect to the received signal and outputs the resulting signal to the RF duplexer 10. To this end, the transmission signal processor 30 includes a second VGA 34, second filter 33, second mixer 32, and power amplifier (PA) 31.
The second VGA 34 performs the variable amplification with respect to the received signal, and the second filter 33 filters an output signal from the second VGA 34 at the IF band or baseband. The second mixer 32 up-converts the frequency of an output signal from the second filter 33, and the PA 31 amplifies the frequency-converted signal and outputs the amplified signal to the RF duplexer 10.
The frequency synthesizer 40 supplies an oscillation signal to each of the first mixer 22 and second mixer 32. To this end, the frequency synthesizer 40 includes a phase locked loop (PLL) circuit 41 and an oscillator 42.
The PLL circuit 41 determines a certain phase, and the oscillator 42 outputs an oscillation signal having a frequency based on the determined phase to each of the first mixer 22 and second mixer 32. In the following drawings including FIG. 1, “RF” means a signal of an RF band, “IF” means a signal of the IF band, and “BB” means a signal of the baseband.
FIG. 2 shows another example of the conventional RF signal transmission/reception apparatus using an RF switch. The RF signal transmission/reception apparatus of FIG. 2 comprises an RF filter 5, a switch 15, a reception signal processor 20, a transmission signal processor 30, a frequency synthesizer 40, and a modem 50.
The operations of the reception signal processor 20, the transmission signal processor 30, the frequency synthesizer 40 and the modem 50 are similar to those stated previously with reference to FIG. 1.
In the example of FIG. 2, the RF filter 5 filters signals of the RF band to be transmitted and received. The switch 15 transfers an RF signal from the RF filter 5 to the reception signal processor 20 or an RF signal from the transmission signal processor 30 to the RF filter 5.
The switch 15 may be implemented by an RF switch which is made with a field effect transistor (FET), PIN diode, or the like.
Accordingly, in the example of FIG. 2, the RF band signals can be processed in a half-duplex transmission manner through the switching of the switch 15.
The communication scheme which performs the transmission and reception simultaneously using the RF duplexer as in FIG. 1 is typically called a full-duplex scheme, and the communication scheme which performs any one of the transmission and reception at one time using the switch as in FIG. 2 is typically called a half-duplex scheme.
However, the conventional RF signal transmission/reception apparatus as in the example of FIG. 1 or FIG. 2 processes signals of the RF band to be transmitted and received, in a duplex manner using the RF duplexer or RF switch, possibly causing problems as follows.
When the RF band signals are processed in the duplex manner using the RF duplexer or RF switch, they may be subject to loss, resulting in a degradation in reception sensitivity. For compensation for the signal loss, it is necessary to raise signal power, causing an increase in power consumption.
Further, the conventional RF signal transmission/reception apparatus as in the example of FIG. 1 or FIG. 2 must have a bulky and costly RF duplexer or RF switch separately from an RF signal transmission/reception chip. Moreover, high-performance, complex RF circuits are required in the reception signal processor and the transmission signal processor, thereby making it difficult to design the circuits of the reception signal processor and the transmission signal processor and increasing the size of the RF signal transmission/reception apparatus. Furthermore, the transmission signal processor and the reception signal processor must also be separately provided, thereby increasing the volume of the RF signal transmission/reception apparatus and making the structure thereof complicated.
In addition, signal interference may occur between RF circuits in the chip of the conventional RF signal transmission/reception apparatus, resulting in a degradation in the entire circuit performance of the apparatus.